E-Thesis 348 views 112 downloads
Developing motorway balancing ponds with long-term net ecological value / STUART CAIRNS
Swansea University Author: STUART CAIRNS
DOI (Published version): 10.23889/SUthesis.63279
Abstract
The contamination of aqueous environments by metals of concern due to anthropogenic factors such as the use of motor vehicles is increasing at an alarming rate, with contaminants such as lead (Pb), copper (Cu), zinc (Zn) and cadmium (Cd) being carried into receiving waterbodies. The sources of vehic...
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Swansea, Wales, UK
2023
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| Institution: | Swansea University |
| Degree level: | Doctoral |
| Degree name: | Ph.D |
| Supervisor: | Robertson, Iain. and Mabbett, Ian. |
| URI: | https://cronfa.swan.ac.uk/Record/cronfa63279 |
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| Abstract: |
The contamination of aqueous environments by metals of concern due to anthropogenic factors such as the use of motor vehicles is increasing at an alarming rate, with contaminants such as lead (Pb), copper (Cu), zinc (Zn) and cadmium (Cd) being carried into receiving waterbodies. The sources of vehicle pollution that contaminate these waterbodies through road runoff are reasonably well understood and the release of the most recognised metals of concern (Pb, Cu, Zn and Cd) are primarily as a result of vehicle abrasion or leaks. Current techniques to remediate motorway runoff, such as balancing ponds, are in place but have the potential to leave toxic residue with the associated removal costs often proving prohibitive.This research focuses on the use of biochar and amended biochar as a remediator for the key metals of concern from motorway run off. The primary aims of this thesis are to: (i) investigate which amendments to biochar improve the immobilisation of Pb, Cu, Zn and Cd (ii) investigate the immobilisation capacities and immobilisation mechanisms of biochar and amended biochar (iii) investigate if amended biochar leaches nutrients harmful to aquatic environments and if so what treatment options are available to mitigate leaching without reducing the immobilisation of Pb, Cu, Zn and Cd, and (iv) to quantify the contact time required for amended biochar to immobilise key metals of concern.Amendments to biochar, particularly wood ash, were found to significantly increase the immobilisation of Pb, Cu, Zn and Cd. Wood ash amended biochar had a maximum measured removal of 61.5 mg/g for Pb, 38.9 mg/g for Cu, 12.1 mg/g for Zn and 10.2 mg/g for Cd, around an order of magnitude greater than pristine biochar. Immobilisation was primarily as a result of precipitation, ion exchange and co-precipitation. When the wood ash was sintered to the biochar, ground to <3mm and rinsed with deionised water the leaching of nutrients, such as phosphates, sulphates and nitrates, fell to below Water Framework Directive thresholds without reducing immobilisation of the metal contaminants. Furthermore, once these treatments were undertaken, the fast removal performance of wood ash amended biochar was still evident with between 86 – 97% of metals being immobilised in the first minute due to precipitation and ion exchange which are key to early stage immobilisation. The results from this research clearly indicate that biochar, specifically wood ash amended biochar has the potential to be scaled up and used to immobilise Pb, Cu, Zn and Cd from motorway runoff as well as from other contaminated aqueous environments such as mine waters. |
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| Item Description: |
A selection of third party content is redacted or is partially redacted from this thesis due to copyright restrictions. |
| Keywords: |
Biochar, motorway, balancing ponds, metals, remediation |
| College: |
Faculty of Science and Engineering |